1. Technical Field
The present invention relates to an automatic reset circuit for a liquid crystal display (LCD) device. In particular, the present invention relates to an automatic reset circuit which removes abnormal driving conditions of an LCD device.
2. Related Art
A liquid crystal display (LCD) device displays an image by controlling an optical transmittance of liquid crystal cells according to an input image signal. An active matrix type LCD device in which a thin film transistor (TFT) is formed at each liquid crystal cell can display a moving image better than a passive matrix type LCD device does.
FIG. 1 is a block diagram showing an LCD device 20 in accordance with the related art. In FIG. 1, the LCD device 20 includes a liquid crystal panel 11 having an upper glass substrate and a lower glass substrate. A liquid crystal is interposed between the upper glass substrate and the lower glass substrate. The liquid crystal panel 11 also includes a plurality of liquid crystal cells 11A, a data driver 12 and a gate driver 13. The data driver 12 supplies data to data lines DL1˜DLm of the liquid crystal panel 11 and the gate driver 13 supplies a scan pulse to gate lines GL1˜GLn of the liquid crystal panel 11.
The gate driver 13 generates a scan pulse by using a timing controller 10, and the generated scan pulse is sequentially supplied to the gate lines GL1˜GLn. The gate driver 13 includes a shift register for sequentially generating a scan pulse, and a level shifter for shifting a swing width of a scan pulse voltage to be suitable for driving the liquid crystal cells 11A.
The data driver 12 samples video data which is input from the timing controller 10 and latches the video data. Subsequently, the data driver 12 converts the latched data into a gamma compensation voltage preset as a pixel data voltage and supplies it to the data lines DL1˜DLm.
The converted data is synchronized in conjunction with each scan pulse every time a scan pulse is generated and is supplied to each of the data lines DL1˜DLm during one horizontal period.
The liquid crystal cells 11A are arranged in a M×N matrix. M data lines DL1˜DLm and N gate lines GL1˜GLn are intersecting one another in the liquid crystal panel 11. A TFT for driving the liquid crystal cell 11A is formed at each intersection.
The TFT is turned on by a scan pulse supplied from the gate driver 13. A data signal on the data lines DL1˜DLm is transmitted to each pixel electrode of the liquid crystal cells 11A.
A gate electrode of the TFT is connected to the same gate line GL1˜GLn at each horizontal line, and a source electrode of the TFT is connected to the same data line DL1˜DLm at each vertical line. Also, a drain electrode of the TFT is connected to each pixel electrode of the liquid crystal cells 11A.
Pixel electrodes of the liquid crystal cells 11A of each horizontal line are partially overlapped with the corresponding previous gate lines GL1˜GLn for driving the liquid crystal cells 11A of the previous horizontal line. As a result, a storage capacitor is formed. For the pixel electrodes of a first horizontal line, a dummy gate line GL0 is used to form a storage capacitor. The dummy gate line GL0 is located above the first gate line GL1 and partially overlaps with the pixel electrodes of the first horizontal line.
A pixel voltage supplied to the data lines DL1˜DLm is charged to a corresponding pixel electrode in response to a gate high voltage of a scan pulse supplied to each gate line GL1˜GLn.
The gate high voltage of a scan pulse is sequentially supplied to the gate lines GL1˜GLn. In response to the gate high voltage, the TFT is turned on and the storage capacitor of the liquid crystal cells 11A is charged with a corresponding pixel voltage. The pixel voltage is input through the data lines DL1˜DLm. The pixel voltage maintains the charged voltage until the TFT is turned on again.
The LCD device 20 is sensitive to external static electricity. Due to the external static electricity, the LCD device 20 may experience abnormal display operations for a short time. Abnormal display operations may result from abnormal turn-on and turn-off of the gate driver 13. Manual reset may resolve the abnormal display operations. After the manual reset, the LCD device 20 recover from abnormal display operations. There is a need of a system that automatically resets the abnormal display operations.